1. Field of the Invention
The present invention relates to a device for producing an optical or acoustic shift instruction in which a speed-of-rotation signal is fed to a first threshold switch for connecting an upshift signal indicator and to a second threshold switch for connecting a downshift signal indicator. Such a device forms the subject matter of Federal Republic of Germany OS No. 29 26 070.
2. Description of the Prior Art
In the known device, a speed-dependent and an engine-load-dependent switch lie in the control circuit of a signal indicator. The engine-load-dependent switch for the upshift signal is opened upon high engine power but closed upon low engine power. This has the result that above a speed of rotation registered by the threshold switch the "upshift" signal appears, provided that the switch which is dependent on the engine load is not opened since the engine power is high at the time and upshifting would be inadvisable inasmuch as the car, for instance, is moving at the time up a hill.
The previously known device for the producing of shift instructions takes into account the physical circumstances of an automotive vehicle which apply for the selection of the time for shifting and represents a signal logic operation. It has the disadvantage, to be sure, that two switches operating as a function of the engine load must be provided. While the speed of rotation of the engine can be readily measured, the production of signals which represent the instantaneous power of the engine affords considerable difficulties. In a carburetor engine one can, to be sure, frequently conclude with a certain amount of accuracy what the engine power is, based on the intake pressure of the carburetor, but a determination of the power in the case of a diesel engine at reasonable expense is out of the question.